Method for reacting flowing liquid and gas in a plasma discharge reactor

ABSTRACT

The activation of the C—H bond using low temperature plasma with an inlet liquid stream such that value added products are formed effectively. An organic liquid (e.g., hexane which is immiscible with liquid water) is injected into a flowing gas (argon) stream followed by mixing with a liquid water stream. Thereafter, the mixture contacts a plasma region formed by a pulsed electric discharge. The plasma formed with the flowing liquid and gas between the two electrodes causes chemical reactions that generate various compounds.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 61/784,149, filed on Mar. 14,2013, titled “Organic Chemical Synthesis Using Plasma Reactors WithLiquid Organic and Liquid Water”, which is hereby incorporated byreference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The present invention was supported by the National Science Foundationgrant CBET 1236225.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates generally to activation of a C—H bond using a lowtemperature plasma and more specifically to activation of a C—H bondusing a low temperature plasma and an inlet liquid stream.

2. Description of the Related Art

Electrical discharge plasma contacting liquid phases has been studiedfor a wide range of chemical, biomedical, environmental, and materialssynthesis applications. The synthesis of a number of organic andinorganic compounds by gas-liquid plasma can involve glow dischargeelectrolysis whereby one electrode is placed inside the liquid phase andone in the gas phase. A wide range of other gas-liquid contactingschemes has been studied including falling films, aerosol sprays, andbubble injection into liquids. It has been shown that the presence ofthe liquid phase not only affects plasma properties such as electronenergy and density, but also the chemical reactions which take place.The liquid phase can also serve as a source of additional vapor phasereactant as well as function as a reservoir to collect the generatedproducts, protecting those products from degradation by direct electronattack in the gas phase plasma. Reactions with organic compounds inplasma discharges have been investigated for a wide range ofapplications and conditions including cases of plasma polymerization,plasma discharge in organic liquids, and the more commonly studied casesof organic compounds in liquid water for pollution control. Plasmagenerated directly in an organic liquid phase has been demonstrated toform diamond coatings and other carbonized materials such as nanofibers.Gas phase plasma (spark discharge: 3 to 12 W) generated with argon overheavy oils (n-C₁₀ to n-C₂₅ hydrocarbons) leads to significant chainbreakage to form one to four carbon containing compounds with ethyleneand hydrogen being the predominate species. Liquid n-hexadecane wasstudied as a model of a hydrocarbon oil and was cracked into C₆ to C₁₅hydrocarbons using a dielectric barrier discharge with a methane carrierover the liquid hydrocarbon. In another example, crude oil was treatedwith a dielectric barrier discharge for various carrier gases (H₂, CO₂,CH₄) where rheological analysis showed a decrease in viscosity of thecrude oil treated by plasma, and NMR analysis showed that the plasmatreatment primarily led to water extraction from the naturally occurringemulsified water in the crude. Finally, an 80 W microwave plasma withwater vapor over a heavy oil liquid demonstrated a series of reactionproducts from long chain aromatics to linear and shorter aromatic ringsand, finally, syngas, CO₂ and small alkanes and alkenes, as well astraces of other carbonaceous products.

Previous studies have also demonstrated efficient production of H₂ frommethanol and water/methanol mixtures, as well as other alcoholsolutions, using a spray reactor. Clearly at high enough plasma powerand exposure time, a wide range of hydrocarbons, even from heavy oils,can be cracked to relatively small compounds. The key issues that willmake these types of applications useful for chemical synthesis ofvaluable products are to control or stop the plasma-induced radicalreactions and to promote reaction selectivity. For example, someselectivity was demonstrated in a gas phase microwave plasma withn-hexane vapor in flowing argon through changes in the plasma inputpower, feed flow rates, and location of the feed.

Oxidation of the C—H group in alkanes under low temperature and pressureconditions is a significant challenge due to selectivity issues and overoxidation by harsh conditions. While catalysts have been developed thatuse hydrogen peroxide to form OH radicals capable of functionalizingalkanes, the reactions are quite complex. Hydrogen abstraction ofalkanes at high temperature primarily for combustion has also beenstudied.

Plasma processes have been demonstrated to produce methanol from methanewith high efficiency. Much of the extensive literature on methaneconversion in plasma reactors focuses on methane conversion in dry gasto higher hydrocarbons and some effort has been devoted towards methaneto methanol and/or formaldehyde conversion with water vapor and orliquid water films.

In plasma discharge in humid gas the direct conversion of methane tomethanol can be expressed by Equation (1):

CH₄+H₂O→CH₃OH+H₂  (1)

The conversion proceeds by the direct reaction of methyl radicals, CH₃,with hydroxyl radicals, OH. In addition to methanol, formaldehyde andformic acid are formed. Using a 500 Hz pulsed discharge reactor atapproximately 400 degrees Celsius and relatively low pressure of 10 to40 Torr, and power of 2 to 6 W, they found methanol yield ofapproximately 0.8% with energy yields of up to 10 g/kWh for glow-likedischarge, but at high voltage spark-like discharge with lower power (5mW) discharge they claim approximately 100 times better efficiency at 1kg/kWh. While the yield is relatively small, the energy efficiency ishigh and may be economically competitive. The reaction kinetics ofmethane oxidation have been extensively studied and include the mainreactions given by Equations (2)-(6):

CH₄+OH→CH₃+H₂O  (2)

CH₃+O₂(+M)→CH₃OO(+M)  (3)

CH₃+HO₂→CH₃O+OH  (4)

CH₃OO+CH₃→CH₃O+CH₃O  (5)

CH₃O+CH4→CH₃OH+CH₃  (6)

As with the formation of hydrogen peroxide and hydrazine, the formationof methanol may be optimized under conditions where degradationreactions with radicals are minimized and over oxidation to CO and CO₂is suppressed.

Alkanes and other compounds have been oxygenated by oxygen radicals inoxygen plasma as well. However, oxidation with hydroxyl radicals fromliquid water in gas-liquid plasma systems has mostly been used tooxidize organic compounds in liquid water for pollution control.Reactions of alkanes such as n-hexane and cyclohexane with OH radicalsproduced from liquid water by plasma discharge where the plasma channelspropagate along a gas-liquid interface have not, to our knowledge, beenreported.

There are three important differences between the functionalization ofhydrocarbons to produce small intermediate products by plasma and themore extensively studied plasma polymerization processes. In plasmapolymerization, the desired goal is to form a surface polymer coatingusing gas phase plasma containing the precursor molecules. In suchcases, a large conversion is required to form the coating. In order toproduce a large conversion, a large plasma energy is required whichleads to complete dissociation of the precursor compounds into smallorganic fragments. The resulting recombination reactions are notsignificantly selective due to the large number of possible reactionswhich can occur. One goal of the present work is to introduceselectivity. Although selectivity may come at the cost of lowerconversion, this cost can be compensated in synthetic chemistry bycomponent recirculation as well as series or parallel reactor designs.The second issue relates to the site of the main polymerizationreactions. In plasma polymerization there is still debate on whether themain polymerization reactions occur in the gas phase or on the surface.Both cases are predicted to lead to the “irregular structure” of thepolymer, where the reactor pressure and plasma pulsing can affect thelocation of these reactions. In gas-liquid plasma systems the physicallocation of the plasma chemical synthesis will depend, in part, on thevolatility of the precursor molecule. Under conditions of lowvolatility, the plasma radicals may directly impinge on the liquidsurface initiating reactions at the interface or even generate someradicals in the liquid phase. For high volatility cases, the organicliquid is fully vaporized and can react directly in the gas phase.Different product distributions are expected in these differentconditions. A third issue relates to modification of reactor/reactionconditions involving generation of pulses by the power supply. Shorterplasma pulses (or with superimposed pressure pulses) have been shown tocontrol chain propagation in plasma polymerization, but again at thecost of yield.

There is a need to utilize a pulsed plasma reactor with a flowing liquidwater film, carrier gas, and various organic compounds for the synthesisof more chemical species.

BRIEF SUMMARY OF THE INVENTION

Various embodiments utilize a pulsed plasma reactor with a flowingliquid water film, carrier gas, and various organic compounds for thesynthesis of more chemical species. The conversion of water intohydrogen peroxide and the normal alkane n-hexane and the cyclic alkanecyclohexane into oxygenated products (alcohols, ketones, and aldehydes)by hydroxyl radical attack was achieved. Reaction products weredetermined by GC-MS and NMR spectroscopy.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims, and accompanying drawings where:

FIG. 1: is a schematic diagram of a process according to variousembodiments;

FIG. 2: shows an illustration of a vertical cross section of the plasmareactor according to various embodiments;

FIG. 3a-d : show illustrations cross sections of various embodiments ofthe plasma reactor;

FIG. 4a-c : are photographs of the plasma discharge with a) rapidshutter speed ( 1/12000 sec) b) a long exposure time ( 1/60 sec), c) aview showing the liquid/gas interface;

FIG. 5: is a sample waveform of discharge;

FIG. 6: is a complete NMR-spectra for sample run with 0.5 ml/min water,0.002 ml/min hexane and 0.5 L/min Argon;

FIG. 7: is a reference spectra for 1-Hexanol and signature peak(triplet, 3.62/3.64);

FIG. 8: is a reference spectra for 2-hexanol and signature peaks(multiplet, 3.79, doublet 1.18);

FIG. 9: is a reference spectra for 3-hexanol and signature peak(multiplet, 3.54);

FIG. 10: is a reference spectra for hexanal and signature peaks(singlet, 9.77, triplet 2.42 merged with quartet);

FIG. 11: shows reference shifts for 2-hexanone and signature peaks(triplet 0.98, singlet 2.15, triplet 2.35/2.38);

FIG. 12: is a reference spectra for 3-hexanone and signature peaks(quartet 2.41, triplet 2.39 merged);

FIG. 13: is a chart showing production rates for 1-hexanol and hexanalas functions of feed flow rates;

FIG. 14: is a chart showing production rates for 2-hexanol and2-hexanone as functions of feed flow rates;

FIG. 15: is a chart showing production rates for 3-hexanol and3-hexanone as functions of feed flow rates;

FIG. 16: is a chart showing formation rate of hydrogen peroxide as afunction of the organic content in the feed for various liquid waterflow rates;

FIG. 17a-c show sample waveforms for the voltage, current, andinstantaneous power of the discharge;

FIG. 18 shows complete NMR-spectra of liquid effluent after extraction,the bottom spectrum representing the starting material (DI water andn-hexane), the top spectrum representing the sample after subjection toplasma discharge;

FIG. 19 shows complete gas chromatogram of liquid effluent afterextraction and solvent evaporation, where the products identified are1-hexanol (4.95 min), 2-hexanol (3.90 min), 3-hexanol (3.68 min),hexanal (2.81 min), 2-hexanone (2.81 min), and 3-hexanone (2.60 min);and

FIG. 20a-b show mean discharge power (a) and production rate of hydrogenperoxide (b) for various n-hexane to water feed ratios, the water flowrate being held constant at 0.5 mL/min while the organic flow rate wasvaried from 0 to 0.002, 0.005, 0.01, 0.02, and 0.04 mL/min.

It should be understood that the various embodiments are not limited tothe arrangements and instrumentality shown in the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention utilizes a gas-water-organic plasma reactor forthe conversion of alkanes into functionalized products (alcohols,aldehydes, etc.) using pulse plasma reactor with liquid water andflowing carrier gas. Hydrogen peroxide is also generated conjunctionwith the functionalized products.

The present invention may be understood more readily by reference to thefollowing detailed description of preferred embodiments of the inventionas well as to the examples included therein. All numeric values areherein assumed to be modified by the term “about,” whether or notexplicitly indicated. The term “about” generally refers to a range ofnumbers that one of skill in the art would consider equivalent to therecited value (i.e., having the same function or result). In manyinstances, the term “about” may include numbers that are rounded to thenearest significant figure.

As discussed above, there is a need to introduce selectivity, butdepending on how this is accomplished it may come at the cost of lowerconversion. Therefore, there is also a need to compensate for the lowerconversion. According to various embodiments of the present invention,lower conversion can be compensated for in synthetic chemistry byreactor recirculation.

As discussed above, there is a need for greater predictability as to thelocation of the main chemical reactions. The physical location of theplasma chemical synthesis according to various embodiments of thepresent invention can depend, in part, on the volatility of theprecursor molecule. Under conditions of low volatility (water), theplasma radicals may directly impinge on the droplet surface initiatingreactions at the interface or even generate some radicals in the liquidphase. For high volatility cases (hexane), the plasma species will reactin the gas phase.

As discussed above, there is a need to provide a modification ofreactor/reaction conditions involving pulsing the power supply. Variousembodiments of the present invention have shown (in the case of H₂O₂)that higher frequency pulses with lower energy per pulse can stronglyincrease energy yields.

According to various embodiments, an organic liquid (e.g., hexane whichis immiscible with liquid water) is injected into a flowing gas (argon)stream followed by mixing with a liquid water stream. Thereafter, themixture contacts a plasma region formed by a pulsed electric discharge.The plasma, which propagates along the interface between the flowingliquid and gas regions between the two electrodes, causes chemicalreactions that generate various compounds. When hexane is used as theorganic precursor NMR spectra clearly show the formation of 1-hexanol,2-hexanol, and 3-hexanol. Indirect evidence strongly suggests theoxygenation is likely due to reaction of OH radicals formed from thisdissociation of water by the plasma. Other spectra indicate theformation of the aldehyde (hexanal) and ketones (2-hexanone and3-hexanone). It is also known that the plasma generates hydrogenperoxide (H₂O₂) by combination of said OH radicals. This workdemonstrates the activation of the C—H bond using low temperature plasmawith an inlet liquid stream such that value added products are formedeffectively. This procedure combines two common chemical feed-stocks(hydrocarbon and water) and transforms them into the higher valuefunctionalized organic products via a sequence of reactions where allnecessary intermediate reactants are formed in situ using the electricdischarge.

FIG. 1 shows a schematic diagram of a process 100 according to variousembodiments. An organic liquid 112, such as n-hexane, can be pumped at aconstant rate via a syringe pump 107, into a first mixing zone 103. Thesyringe pump 107 can have a 10 mL glass syringe. The first mixing zone103 can be a nylon Swagelok tee joint. High pressure argon can be addedto the first mixing zone 103 from a high pressure argon storagecontainer 106 via a pressure regulator 105 where the flow rate ismeasured by a rotameter 104. Subsequently the organic liquid and thehigh pressure argon in the first mixing zone 103 can pass into a secondmixing zone 102. The second mixing zone 102 can be a nylon Swagelok teejoint. DI water 113 can be pumped via a high-pressure pulse injectionpump 101 into a second mixing zone 102. All of the contents of thesecond mixing zone, the organic liquid, the argon, and the DI water canbe added to a reactor 109. The reactor 109 includes a plasma dischargeregion 114. Emission spectroscopy and/or high speed imaging 115 can beperformed on the reactor 109. A high voltage (HV) probe 108 can be usedto measure the voltage applied to the reactor. At the outlet of thereactor a shunt 110 can be used to measure the electrical current andthereby in combination with the voltage determine the power delivered tothe reactor. A liquid effluent trap 111 can be used to collect theliquid exiting the reactor for subsequent chemical analysis. A powersource 116 can supply a voltage at least one electrically-conductiveinlet capillary and at least one electrically-conductive outletcapillary of the reactor 109, which are illustrated in greater detail inFIG. 2. Primary 117 and secondary 118 cold traps consisting of dry iceand acetone can also be employed to condense vaporized products notcollected in the liquid effluent trap prior to the gas effluent exit119.

FIG. 2 shows an illustration of a vertical cross section of the plasmareactor 109 according to various embodiments. FIG. 2 shows a verticalcross section diagram of the reactor 109. Because of its simpleconstruction from pre-fabricated materials, an added benefit to thisreactor design is that it can be considered “disposable.”

The reactor 109 can include a body portion 217 having one or moreinternal walls 213, 214 that define an internal cavity 215. According tovarious embodiments, and as shown in FIG. 2, the body portion 217 can becylindrical.

The reactor 109 can include at least one electrically-conductive inletcapillary 201 having an inlet capillary body 207 extending between afluid-receiving tip 208 and a fluid-injecting tip 209. Thefluid-receiving tip 208 is positioned outside the internal cavity 215,and the fluid-injecting tip 209 is positioned inside the internal cavity215.

The reactor can include at least one electrically-conductive outletcapillary 205 having an outlet capillary body 210 extending between afluid-collecting tip 211 and a fluid-ejecting tip 212. Thefluid-collecting tip 211 is positioned inside the internal cavity 215,and the fluid-ejecting tip 212 is positioned outside the internal cavity215. The electrically-conductive inlet capillary 201 and theelectrically-conductive outlet capillary 205 can be made of anyelectrically conductive material, for example, according to oneparticularly preferred embodiment the electrically-conductive inletcapillary 201 and the electrically-conductive outlet capillary 205 canbe made a 316 stainless steel capillary tubing with an outer diameter(O.D.) of 1.59 mm (Restek). Other electrically-conductive materials, asdescribed herein can also be employed. The capillaries can also be anyshape, but are preferably cylindrical.

The fluid injecting tip 209 can be disposed relative to the fluidcollecting tip 211 to generate a flowing liquid film region 203 on theone or more internal walls 213, 214 and a gas stream or a gas flowregion 202 flowing through the flowing liquid film region 203, when afluid is injected into the internal cavity 215 via the at least oneelectrically conductive inlet capillary 201. The fluid injecting tip 209can be disposed relative to the fluid collecting tip 211 to propagate aplasma discharge along the flowing liquid film region 203 between the atleast one electrically-conductive inlet capillary 201 and the at leastone electrically-conductive outlet capillary 205. According to variousembodiments, the fluid injecting tip 209 can be aligned with the fluidcollecting tip 211.

According to particularly preferred embodiments, the internal walls 213,214 can be the inner walls of a piece of fused quartz tubing 204 with anI.D. of 3.0 mm (AdValue Technology) which can serve as a viewing portfor emission spectroscopy and high speed imaging. According to otherparticularly preferred embodiments, the electrically-conductive inletcapillary 201 and the electrically-conductive outlet capillary 205 canbe incased by fused quartz tubing spacers 206 with an I.D. of 1.6 mm(AdValue Technology); the tubing 206 can be positioned such that theends of the stainless steel and quartz tube spacers are flush at theentrance and exit of the discharge region, i.e. the internal cavity 215.These inlet and outlet assemblies comprising the electrically-conductiveinlet capillary 201 and the electrically-conductive outlet capillary 205incased by fused quartz tubing spacers 206 can then inserted into eitherend of the tubing 204.

The fluid injecting tip 209 and the fluid collecting tip 211 (or whenemployed, the respective ends of the inlet and outlet assemblies) can bepositioned such that a gap 216 having a length. The gap 216 can have alength within a range having a lower limit and/or an upper limit. Therange can include or exclude the lower limit and/or the upper limit. Thelower limit and/or upper limit can be selected from 0.1, 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9,2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4,3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9,5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4,6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9,8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4,9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7,10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9,12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13, 13.1,13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14, 14.1, 14.2, 14.3,14.4, 14.5, 14.6, 14.7, 14.8, 14.9, 15, 15.1, 15.2, 15.3, 15.4, 15.5,15.6, 15.7, 15.8, 15.9, 16, 16.1, 16.2, 16.3, 16.4, 16.5, 16.6, 16.7,16.8, 16.9, 17, 17.1, 17.2, 17.3, 17.4, 17.5, 17.6, 17.7, 17.8, 17.9,18, 18.1, 18.2, 18.3, 18.4, 18.5, 18.6, 18.7, 18.8, 18.9, 19, 19.1,19.2, 19.3, 19.4, 19.5, 19.6, 19.7, 19.8, 19.9, 20, 20.1, 20.2, 20.3,20.4, 20.5, 20.6, 20.7, 20.8, 20.9, 21, 21.1, 21.2, 21.3, 21.4, 21.5,21.6, 21.7, 21.8, 21.9, 22, 22.1, 22.2, 22.3, 22.4, 22.5, 22.6, 22.7,22.8, 22.9, 23, 23.1, 23.2, 23.3, 23.4, 23.5, 23.6, 23.7, 23.8, 23.9,24, 24.1, 24.2, 24.3, 24.4, 24.5, 24.6, 24.7, 24.8, 24.9, and 25 mm. Forexample, according to certain preferred embodiments, the gap 216 canhave a length of about 4 mm.

The reactor can also include a power source 116, supplying a voltageacross the at least one electrically-conductive inlet capillary and theat least one electrically-conductive outlet capillary. The power source116 can be adapted to provide a pulsed current, a D.C. current, and/oran A.C. current between the at least one electrically-conductive inletcapillary 201 and the at least one electrically-conductive outletcapillary 205.

A ratio of the voltage to the length of the gap 216 can be within arange having a lower limit and/or an upper limit. The range can includeor exclude the lower limit and/or the upper limit. The lower limitand/or upper limit can be selected from 2.5×10⁵ V/m, 3×10⁵, 4×10⁵,5×10⁵, 6×10⁵, 7×10⁵, 8×10⁵, and 9×10⁵ V/m. For example, the body portion217 can have a length, and a ratio of the voltage to the length can beat least about 2.5×10⁵ V/m.

According to various embodiments, the body portion 217 can becylindrical. The cylindrical body portion 217 can have a first diameterwithin a range having a lower limit and/or an upper limit. The range caninclude or exclude the lower limit and/or the upper limit. The lowerlimit and/or upper limit can be selected from 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16,0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28,0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4,0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52,0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, 0.61, 0.62, 0.63, 0.64,0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76,0.77, 0.78, 0.79, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88,0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1,1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12,1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.21, 1.22, 1.23, 1.24,1.25, 1.26, 1.27, 1.28, 1.29, 1.3, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36,1.37, 1.38, 1.39, 1.4, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48,1.49, 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.6,1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.7, 1.71, 1.72,1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79, 1.8, 1.81, 1.82, 1.83, 1.84,1.85, 1.86, 1.87, 1.88, 1.89, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96,1.97, 1.98, 1.99, and 2 cm. For example, according to certain preferredembodiments, the cylindrical body portion 217 can have a first diameter0.1 to 1 cm. The at least one electrically-conductive inlet capillarycan have a second diameter that is less than the first diameter. The atleast one electrically-conductive outlet capillary can have a thirddiameter that is greater than the second diameter and less than thefirst diameter.

FIG. 3a shows an illustration of a radial cross section along line A-Aas shown in FIG. 2 of the plasma reactor 109 according to variousembodiments. A horizontal cross section of the discharge region is shownin FIG. 3. The gas flow region 202 can be bounded by a gas/liquidinterface 301, separating the gas flow and plasma discharge region 202from the liquid film flow region 203. The gas/liquid interface 301 canbe, but need not always be highly turbulent. As discussed under FIG. 2,the liquid film flow region 203 flows along the fused quartz tubing 204which acts as the reactor wall.

According to various embodiments, the gas flow can be determined by thenozzle, i.e. the outlet of a capillary, diameter and the pressure. Theliquid flow can be determined by the gas flow, and all other dependentproperties can thereafter be determined. The maximum liquid flow can bedetermined by the gas flow, and all other dependent properties canthereafter be determined. The pressure of the inlet gas can be in therange of 10 to 500 pounds per square inch (psi). For an inlet gaspressure of 60 psi and a 0.01 inch inlet capillary nozzle with a 3 mmtube, the gas flow is 0.3 liters per minute and the upper liquid flowcan be 4 ml/min. In addition to scaling up this process up by placingmany single reactors in parallel, alternative geometries could be usedwhich utilize a single large volume chamber for the flow of water andgas in conjunction with multiple inlet and outlet nozzles into and outof the single chamber.

FIG. 3b shows an illustration of a radial cross section of an exemplaryconfiguration comprising a reactor body 302 and a plurality ofelectrically-conductive inlet capillaries 303. The reactor body 302 isan annular ring and has a distance D between its walls. Each of theelectrically-conductive inlet capillaries 303 can have a range ofinfluence 304 within the reactor body 302. Inside its range of influenceeach electrically-conductive inlet capillary can be used to form aplasma discharge. One or more electrically-conductive outlet capillaries(not shown) can be aligned with or otherwise positioned relative to theplurality of electrically-conductive inlet capillaries 303 to generate aflowing liquid film region on one or more internal walls of the reactorbody 302 and a gas stream or a gas flow region flowing through theflowing liquid film region, when a fluid is injected into the internalcavity via the at least one electrically conductive inlet capillary 303.The one or more electrically-conductive outlet capillaries (not shown)can additionally or alternatively be aligned with or otherwisepositioned relative to the plurality of electrically-conductive inletcapillaries 303 to propagate a plasma discharge along the flowing liquidfilm region between one or more of the plurality ofelectrically-conductive inlet capillaries 303 and one or more of the oneor more plurality of electrically-conductive outlet capillaries. Asshown, a gas liquid interface 305 can be generated between a liquid filmregion 307 and a gas flow region 306 passing across the liquid filmregion 307.

FIG. 3c shows an illustration of a radial cross section of an exemplaryconfiguration comprising a reactor body 308 and a plurality ofelectrically-conductive inlet capillaries 309. The reactor body 308 isan elongated box and has a distance D between its walls. Each of theelectrically-conductive inlet capillaries 309 can have a range ofinfluence 310 within the reactor body 308. Inside its range of influenceeach electrically-conductive inlet capillary can be used to form aplasma discharge. One or more electrically-conductive outlet capillaries(not shown) can be aligned with or otherwise positioned relative to theplurality of electrically-conductive inlet capillaries 309 to generate aflowing liquid film region on one or more internal walls of the reactorbody 308 and a gas stream or a gas flow region flowing through theflowing liquid film region, when a fluid is injected into the internalcavity via the at least one electrically conductive inlet capillary 309.The one or more electrically-conductive outlet capillaries (not shown)can additionally or alternatively be aligned with or otherwisepositioned relative to the plurality of electrically-conductive inletcapillaries 309 to propagate a plasma discharge along the flowing liquidfilm region between one or more of the plurality ofelectrically-conductive inlet capillaries 309 and one or more of the oneor more plurality of electrically-conductive outlet capillaries. Asshown, a gas liquid interface 311 can be generated between a liquid filmregion 312 and a gas flow region 313 passing through the liquid filmregion 312.

Any configuration of the reactor body can be employed. Theconfigurations shown in FIG. 2, FIG. 3a , FIG. 3b , and FIG. 3c aremerely exemplary. Any geometry can be employed.

FIG. 3d shows a vertical cross-section of a reactor body 308 as depictedin either FIG. 3b or 3 c. Since the vertical cross section would be thesame for both the reactor body could have been designated with referencenumeral 302. Reference numerals in the specific embodiment shown in FIG.3d correspond to those in FIG. 3c . Again, since the vertical crosssection would be the same for FIG. 3b , the reference numerals of FIG.3b could have been used. FIG. 3d also shows a plurality ofelectrically-conductive outlet capillaries 314. Theelectrically-conductive outlet capillaries 314 are shown in alignmentwith the electrically-conductive inlet capillaries 309. FIG. 3c alsoillustrates a length L of the reactor body 308.

Various embodiments relate to a method comprising injecting a mixturecomprising liquid water, a gas, and an organic compound, into at leastone electrically-conductive inlet capillary tube of acontinuously-flowing plasma reactor to generate a flowing liquid filmregion on one or more internal walls of the continuously-flowing plasmareactor with a gas stream flowing through the flowing liquid filmregion; propagating a plasma discharge along the flowing liquid filmregion from at least one electrically-conductive inlet capillary to anelectrically-conductive outlet capillary tube at an opposing end of thecontinuously-flowing plasma reactor; dissociating the liquid water inthe plasma discharge to form a plurality of dissociation products;producing hydrogen peroxide from the plurality of dissociation products;dissolving the hydrogen peroxide into the flowing liquid film region;and recovering at least a portion of the hydrogen peroxide from theelectrically conductive outlet capillary.

The mixture can be injected into a plurality of electrically-conductiveinlet capillary tubes. The flowing liquid film region can have anannular shape. The gas stream can flow through the center of the flowingliquid film region. For example, the gas stream can flow through acentral portion of the annularly shaped flowing liquid film region.

The plasma discharge can have a nominal frequency within a range havinga lower limit and/or an upper limit. The range can include or excludethe lower limit and/or the upper limit. The lower limit and/or upperlimit can be selected from 400, 405, 410, 415, 420, 425, 430, 435, 440,445, 450, 455, 460, 465, 470, 475, 480, 485, 490, 495, 500, 505, 510,515, 520, 525, 530, 535, 540, 545, 550, 555, 560, 565, 570, 575, 580,585, 590, 595, and 600 Hz. For example, according to certain preferredembodiments, the plasma discharge can have a nominal frequency of 500Hz.

The plasma discharge can have a frequency within a range having a lowerlimit and/or an upper limit. The range can include or exclude the lowerlimit and/or the upper limit. The lower limit and/or upper limit can beselected from 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160,170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200,1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400,2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600,3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800,4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000,6100, 6200, 6300, 6400, 6500, 6600, 6700, 6800, 6900, 7000, 7100, 7200,7300, 7400, 7500, 7600, 7700, 7800, 7900, 8000, 8100, 8200, 8300, 8400,8500, 8600, 8700, 8800, 8900, 9000, 9100, 9200, 9300, 9400, 9500, 9600,9700, 9800, 9900, 10000, 10100, 10200, 10300, 10400, 10500, 10600,10700, 10800, 10900, 11000, 11100, 11200, 11300, 11400, 11500, 11600,11700, 11800, 11900, and 12000 Hz. For example, according to certainpreferred embodiments, the plasma discharge can have a frequency of fromabout 100 to 10000 Hz.

According to various embodiments, the method can further includegenerating at least one functionalized product from the organic liquidand the plurality of dissociation products in the plasma discharge. Thefunctionalized product can be, but is not limited to an alcohol, aketone, an aldehyde, an ester, an organic acid, an organic peroxide, andcombinations thereof. For example, the functionalized product can analcohol, including but not limited to methanol, hexanol, decanol,cyclohexanol, phenol, phenethyl alcohol, benzyl alcohol, andcombinations thereof. For example, the functionalized product can be aketone, including but not limited to butanone, hexanone, cyclopentanone,cyclohexanone, propiophenone, benzophenone, and combinations thereof.For example, the functionalized product can be an aldehyde, includingbut not limited formaldehyde, hexanal, cyclopentanal, cyclohexanal,benzaldehyde, tolualdehyde, and combinations thereof. For example, thefunctionalized product can be an ester, including but not limited toethyl acetate, ethyl formate, ethyl isovalerate, isobutyl acetate,propyl isobutyrate, ethyl acetate, benzyl acetate, methyl phenylacetate,and combinations thereof. For example, the functionalized product can bean organic acid, including but not limited to acetic acid, butyric acid,hexanoic acid, cyclohexanecarboxylic acid, benzoic acid, andcombinations thereof. For example, the functionalized product can be anorganic peroxide, including but not limited to peracetic acid,hydroperoxyhexane, methyl hydroperoxide, cyclohexane peroxide, benzoylperoxide, and combinations thereof.

According to other embodiments, the method can further includerecovering the generated hydrogen peroxide and the functionalizedorganic products. According to various embodiments, the hydrogenperoxide dissolved into the flowing liquid film region can be protectedfrom degradation as the hydrogen peroxide flows through the flowingliquid film region and exits the continuously-flowing plasma reactor viathe electrically conductive outlet capillary.

The liquid water can have a temperature within a range having a lowerlimit and/or an upper limit. The range can include or exclude the lowerlimit and/or the upper limit. The lower limit and/or upper limit can beselected from 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7,7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5,15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5,22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5,29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5,36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41, 41.5, 42, 42.5,43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5,50, 50.5, 51, 51.5, 52, 52.5, 53, 53.5, 54, 54.5, 55, 55.5, 56, 56.5,57, 57.5, 58, 58.5, 59, 59.5, 60, 60.5, 61, 61.5, 62, 62.5, 63, 63.5,64, 64.5, 65, 65.5, 66, 66.5, 67, 67.5, 68, 68.5, 69, 69.5, 70, 70.5,71, 71.5, 72, 72.5, 73, 73.5, 74, 74.5, 75, 75.5, 76, 76.5, 77, 77.5,78, 78.5, 79, 79.5, 80, 80.5, 81, 81.5, 82, 82.5, 83, 83.5, 84, 84.5,85, 85.5, 86, 86.5, 87, 87.5, 88, 88.5, 89, 89.5, 90, 90.5, 91, 91.5,92, 92.5, 93, 93.5, 94, 94.5, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5,99, 99.5, 100, 100.5, 101, 101.5, 102, 102.5, 103, 103.5, 104, 104.5,105, 105.5, 106, 106.5, 107, 107.5, 108, 108.5, 109, 109.5, 110, 110.5,111, 111.5, 112, 112.5, 113, 113.5, 114, 114.5, 115, 115.5, 116, 116.5,117, 117.5, 118, 118.5, 119, 119.5, and 120 degrees Celsius. Forexample, according to certain preferred embodiments, the liquid watercan have a temperature of from greater than 0 to less than 100 degreesCelsius.

The reactor can have a pressure within a range having a lower limitand/or an upper limit. The range can include or exclude the lower limitand/or the upper limit. The lower limit and/or upper limit can beselected from 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45,0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1,1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75,1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4,2.45, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3, 3.05,3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7,3.75, 3.8, 3.85, 3.9, 3.95, and 4 bar. For example, according to certainpreferred embodiments, the reactor can have a pressure of fromapproximately 0.1 to 2 bar.

The liquid water has a conductivity within a range having a lower limitand/or an upper limit. The range can include or exclude the lower limitand/or the upper limit. The lower limit and/or upper limit can beselected from 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145,150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215,220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285,290, 295, 300, 305, 310, 315, 320, 325, 330, 335, 340, 345, 350, 355,360, 365, 370, 375, 380, 385, 390, 395, 400, 405, 410, 415, 420, 425,430, 435, 440, 445, 450, 455, 460, 465, 470, 475, 480, 485, 490, 495,500, 505, 510, 515, 520, 525, 530, 535, 540, 545, 550, 555, 560, 565,570, 575, 580, 585, 590, 595, 600, 605, 610, 615, 620, 625, 630, 635,640, 645, 650, 655, 660, 665, 670, 675, 680, 685, 690, 695, and 700microSiemens/cm. For example, according to certain preferredembodiments, the liquid water has a conductivity 1 to 500microSiemens/cm.

The gas can be a diatomic gas, a noble gas, and combinations thereof.The diatomic gas can be hydrogen, nitrogen, fluorine, oxygen, iodine,chlorine, bromine, and combinations thereof. The noble gas can behelium, neon, argon, krypton, xenon, radon, and combinations thereof.

The organic liquid can be an alkane, an alkene, an aromatic hydrocarbon,and combinations thereof. The alkane can have a structure selected fromlinear, cyclic, branched, and combinations thereof. The alkane can be aC1-C20 alkane. The alkane can be, but is not limited to, methane,ethane, propane, butane, hexane, octane, decane, Icosane andcombinations thereof. The alkene can have a structure selected fromlinear, cyclic, branched, and combinations thereof. The alkene can be aC2-C20 alkene. The alkene can be, but is not limited to ethylene,propylene, hexenes, octenes, decenes, pentadecenes and combinationsthereof. The aromatic hydrocarbon can include from 6 to 20 carbon atoms.The aromatic hydrocarbon can be, but is not limited to, benzene,toluene, ethylbenzene, xylenes, cumene, biphenyl, anthracene, andcombinations thereof.

The at least one electrically-conductive inlet capillary and the atleast one electrically-conductive outlet capillary can include anelectrically conductive material. The electrically conductive materialcan be, but is not limited to stainless steel, nickel alloys, chromiumalloys, titanium alloys, molybdenum alloys, copper alloys, gold alloys,platinum alloys, zinc alloys, zirconium alloys, and combinationsthereof.

FIGS. 4a, 4b, and 4c depict high speed imaging of the plasma dischargeregion. FIG. 4a shows a single plasma channel 400 propagating betweenelectrodes and along the gas liquid interface. FIG. 4b , with a longphotographic exposure, shows multiple plasma channels 400, 401, and 402propagating between electrodes. FIG. 4c shows a liquid film region 403,and a gas flow region 404, separated by a liquid/gas interface 405. Aplasma discharge 406 is also shown at the liquid/gas interface 405.

The invention is further described in the following illustrativeexamples in which all parts and percentages are on a molar basis unlessotherwise indicated.

Examples

According to the present disclosure, vaporized n-hexane in a flowingargon carrier gas was mixed with deionized liquid water and injectedinto a tubular plasma reactor. A liquid water film forms on the wall ofthe tubular reactor and plasma channels propagate along the gas-liquidinterface. Gas-chromatography mass spectrometry (GC-MS) and nuclearmagnetic resonance (NMR) spectroscopic analysis of the major productsand their relative ratios collected in the effluent of the reactorconfirm the formation of 3-hexanol (26%), 2-hexanol (21%), 3-hexanone(17%), 2-hexanone (17%), 1-hexanol (11%), and hexanal (8%). Thefunctionalization is likely due to oxidation of the organic statingmaterial by OH radicals formed from the dissociation of water by theplasma. The functionalization of cyclohexane was achieved in the samemanner where analysis showed the formation of cyclohexanone (47%),cyclohexene (20%), cyclohexanol (19%), hexanal (11%), and2-cyclohexenone (2%). Hydrogen peroxide was also produced in thepresence of either organic compound and the amount formed decreased asthe amount of organic flowing into the reactor was increased. It islikely that the hydrogen peroxide is formed in the gas phase close tothe gas-liquid interface by OH radical recombination. This workdemonstrates the activation of the C—H bond using low temperature plasmaby combining two common chemical feed-stocks (hydrocarbon and water) andtransforming them into the higher value functionalized organic productsvia a sequence of reactions where all necessary intermediate reactantsare formed in situ by the electric discharge.

Reactor and Apparatus

The Examples employ a process as illustrated in FIG. 1, which shows thegeneral process schematic of the experimental setup. High purity argongas (Air Gas; Tallahassee, Fla.) at 414 kPa was utilized, resulting in aflow rate of 0.5 L/min as measured by a rotameter (Cole Palmer; VernonHills, Ill.). The argon was allowed to flow unrestricted into thereactor inlet. The argon flow rate is a function of the pressure headand the inner diameter (I.D.) of the reactor inlet nozzle (0.25 mm). Theargon gas contacts a small amount of liquid organic such as n-hexane orcyclohexane at Mixing Zone 1 which was a 1/16″ Swagelok® nylon teejoint, Jax Fluid System Technologies; Jacksonville, Fla. The liquidorganic was pumped at a constant rate of 0.002 mL/min with a syringepump (Harvard Apparatus, PhD 2000 Infusion; Holliston, Mass.) equippedwith a 10 mL glass syringe (Hamilton, GASTIGHT; Reno, Nev.).

Due to the small amount of n-hexane or cyclohexane used in comparison tothe argon flow rate and their high volatility, the organic liquidrapidly vaporized into the gas phase. The process can be easily adaptedto utilize organic liquids other than n-hexane or cyclohexane. Theresulting gas phase mixture then contacts a liquid stream of deionizedwater flowing at 0.5 mL/min (pH—5.0±0.2, conductivity—5.0±1.0 μS/cm) atMixing Zone 2 ( 1/16″ Swagelok® nylon tee joint, Jax Fluid SystemTechnologies; Jacksonville, Fla.). The deionized water was delivered tothe system with a high pressure, pulse injection pump (Optos Series,Eldex Laboratories Inc.; Napa, Calif.).

High pressure mixing occurs between these three components (argon,organic, and water) in Mixing Zone 2, after which the mixture flowsthrough the inlet nozzle of the reactor and into the plasma dischargeregion where chemical reactions are induced.

After exiting the discharge region, the liquid phase of the effluent wasdirectly collected in a vessel while the gas phase was allowed to flowthrough a series of condensers submerged in cold baths consisting of dryice and acetone (−78° C.) in order to condense out any compounds stillvaporized in the argon gas. A four hour run time was utilized whereafterwards the resulting three liquid phases were analyzed individuallyusing GC-MS, NMR and UVis spectroscopy.

The reactor was constructed from pre-fabricated round tubing giving it acylindrical geometry. FIG. 2 shows a vertical cross section diagram ofthe reactor. Because of its simple construction from pre-fabricatedmaterials, an added benefit to this reactor design is that it can beconsidered “disposable.” The inlet and outlet parts of the reactor aremade of 316 stainless steel capillary tubing with an outer diameter(O.D.) of 1.59 mm (Supelco; Bellefonte, Pa.) and are incased by fusedquartz tubing spacers with an inner diameter (I.D.) of 1.6 mm (AdValueTechnology; Tucson, Ariz.); the tubing was positioned such that the endsof the stainless steel and quartz tube spacers were flush at theentrance and exit of the discharge region. The inlet and outletassemblies were then inserted into either end of an additional piece offused quartz tubing with an I.D. of 3.0 mm (AdValue Technology; Tucson,Ariz.) which served as the reactor wall and viewing port for emissionspectroscopy and high speed imaging. The inlet and outlet assemblieswere positioned such that a 4 mm gap existed between the entrance andexit of the discharge region. A horizontal cross section of thedischarge region is shown in FIG. 3 a.

A key aspect of this reactor system is the flow pattern generated insidethe reactor volume. Because the inlet capillary tube has an internaldiameter (I.D.) of 0.25 mm and that of the discharge region is 3 mm, awell-mixed radial spray is generated as the high pressure mixture exitsthe inlet nozzle and enters the reactor volume. Due to the constrictionat the reactor inlet, high pressure mixing occurs between the componentswhich exit from Mixing Zone 2 in FIG. 1. Because the inlet capillarytube has an inner diameter of 0.25 mm and that of the discharge regionis 3 mm, a well-mixed radial spray is generated as the high pressuremixture exits the inlet capillary and enters the reactor volume. Thisspray then rapidly contacts the reactor wall creating a liquid filmwhich flows along the reactor wall coupled with a high velocity gas flowregion in the radial center of the reactor.

High speed imaging was performed with a VW-9000 series high speedmicroscope system with a VH-00R 0-50× lens (Keyence; Itasca, Ill.) toconfirm the existence and analyze the previously mentioned flow regions.FIG. 4a is a photograph of the reaction plasma zone region taken with arapid shutter speed ( 1/12000 sec) and captures not only a singlefilamentous plasma channel, but also the wave-like pattern of water flowon the walls of the reactor. FIG. 4b depicts a long exposure time ( 1/60sec) and captures the many filamentous plasma channels produced duringthis time period. Both photos (FIGS. 4a and 4b ) indicate that thedischarge takes place along the gas-liquid interface and not within theliquid film flow region or in the middle of the gas stream; the majorityof the plasma streamers appear to travel along the gas liquid interface.In FIG. 4b the reddish streamer channels arise from the water flow whilethe lighter bluish-green parts come from the organic vapor.

An additional key aspect of this reactor design was that the stainlesssteel capillary tubing which acted as the entrance and exit to thereactor volume also function as the anode and cathode which generate theplasma discharge as shown in FIG. 1. This configuration provides maximumcontact of the reactants with the plasma by minimizing by-pass regionswhere the gas-liquid flow does not contact the plasma. In the specificsetup the high voltage lead was attached to the inlet nozzle of thereactor while the outlet capillary was grounded. The power supply andpulse forming circuit is similar to that used in our previous work. Thepower supply (DC 1740B BK Precision; Yorba Linda, Calif.) was driven bya pulse generator (2 MHz 4010A BK Precision; Yorba Linda, Calif.) toprovide pulsed 12 V direct current to an automobile ignition coil(VW-AG, ERA Germany). A high voltage diode was placed between theignition coil and the reactor to protect the coil from unwanted upstreamvoltage surges back to the ignition coil from the reactor. The pulsefrequency and duty cycle was held constant for all experiments at 500 Hzand 40%.

The voltage, current, and power waveforms of the discharge were measuredwith a Tektronix DPO 3014 oscilloscope (Tektronix Inc.; Beaverton,Oreg.). The sampling rate of the oscilloscope was 10⁴ points for the 100ms acquisition window. The discharge voltage was measured with ahigh-voltage probe (P6015 Tektronix; Beaverton, Oreg.) connected to thelead electrode. The current was measured with a 100Ω shunt to the groundin the secondary of the ignition coil. The math function of theoscilloscope was used to generate the calculated power pulses. FIG. 5 isa screen shot of a measurement from said oscilloscope 500. Power 502(watts) is shown in red, current 503 (amps) is shown in green, andvoltage 501 (volts) is shown in yellow. Averages of three powermeasurements for each trial were taken to reduce the error of themeasurement and exported to Excel where the magnitude of the individualdata points were averaged to provide a mean power for the time period ofthe acquisition window. The instantaneous power was calculated bymultiplication of the individual data points in the current and voltagewaveforms. The mean discharge power was determined by averaging theinstantaneous power across the time period of acquisition window. Samplecurrent, voltage, and power waveforms are shown in FIGS. 17a-c . Itshould be noted that the power reported in this study was the “powerdelivered to the discharge” and that the overall efficiency also dependsupon the power and efficiency of the transformer.

After exiting the reactor the liquid and gas effluent are separated andanalyzed using NMR and Gas Chromatography.

NMR and Chemical Analysis

A vial containing 30 ml of sample from the reactor—consisting of only anaqueous layer—is extracted with 1 ml of deuterated chloroform, which isthen retrieved and pipetted into an empty NMR test tube. The sameprocedure is repeated on a reference sample based on the same flow ratesof hexane, water and argon but without activated plasma discharge.Subsequently, both spectra are compared in order to distinguish productsfrom prevalent impurities in the starting materials (FIG. 6). FIG. 6 isa complete NMR-spectra 600 for sample run with 0.5 ml/min water, 0.002ml/min hexane and 0.5 L/min Argon. Item 602 shown in red indicates thecontrol sample not exposed to the electrical discharge. Item 601 shownin blue indicates a liquid sample collected downstream of the electricaldischarge reactor in the liquid effluent trap shown in FIG. 1 as 111.The NMR acquisition time of 1 hour (1000 runs) provides sharp 1H protonNMR spectra. The NMR system was a Bruker 600 MHz Ultrashield. Referencespectra are obtained mostly from the “Spectral Database of OrganicCompounds, SDBS” organized by the National Institute of AdvancedIndustrial Science and Technology (AIST), Japan(http://sdbs.riodb.aist.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng),unless otherwise stated.

The concentration of hydrogen peroxide formed in the liquid fractionswas measured using a colorimetric test with a UV-Vis spectrophotometer(Perkin-Elmer, Lambda 35; Waltham, Mass.) where 2 mL liquid samples weretaken and mixed with 1 mL of a titanium oxysulfate-sulfuric acidcomplex. The absorbance of the formed yellow complex was measured at a410 nm wavelength and converted to hydrogen peroxide concentration by acalibration curve generated with stock solutions of hydrogen peroxidewhere concentration was confirmed by titration with 0.1 N potassiumpermanganate.

For GC-MS analysis, the three separate aqueous fractions collected fromthe reactor were combined, extracted with chloroform, and dried oversodium sulfate. The resulting extract was then left open to theatmosphere for a period of time in order to concentrate the products bysolvent evaporation. The analysis was performed on a Clarus 500 GC withan Elite-Wax column length of 30 m and diameter size of 250 μm inconjunction with a Clarus 550d MS (Perkin Elmer). Standards of theidentified products as well as the starting materials were utilized toprovide additional verification for the identified compounds.

For NMR analysis, successive extractions on the three separate aqueousfractions collected from the reactor were performed with deuteratedchloroform and the resulting extracts dried over sodium sulfate.Analysis of each individual fraction was executed with a 600 MHzUltrashield (Bruker) where an acquisition time of 1 hour was utilized.Identification of the product compounds was performed by comparing thechemical shift and the multiplicity of key NMR signature peaks of theparticular compound to reference NMR spectra obtained from the “SpectralDatabase of Organic Compounds, SDBS” organized by the National Instituteof Advanced Industrial Science and Technology, Japan. In most cases thesignature peaks originated from functional groups bonded closely to themain characteristic functional group, i.e. CH₃ bonded to a carbonylgroup. A quantitative analysis on the three liquid fractions collectedwas also performed with NMR by adding known concentrations of benzylphenyl ether to the three separate extracts of the aqueous phases. Theintegrated signals of all functional groups of interest were thencompared with the integrated singlet signal of the benzyl phenyl etherCH₂-group at 5.05 ppm to allow the back calculation of the concentrationof each compound.

Results

FIGS. 7 to 12 show example NMR spectra demonstrating the presence ofreaction products from hexane. The main products identified are1-hexanol, 2-hexanol, 3-hexanol, hexanal, 2-hexanone, and 3-hexanone.Additional products showing other NMR peaks not illustrated here havenot yet been identified. The identification of the product compounds wasperformed by comparing the NMR shift as well as the multiplicity of keysignature peaks of the particular compound. Usually the signature peaksoriginate from functional groups bonded closely to the main functionalgroup, i.e. CH₃ bonded to a carbonyl group or CH₂ directly bonded to theoxygen of an alcohol. Peaks from other parts of the molecule usuallycannot be used for identification since they overlap with very similargroups from other products.

FIG. 7 shows the formation of 1-hexanol (blue from our reactor) bycomparison of the triplet signature peaks 701 centered around 3.64 ppmwith the reference spectra 700 taken from the literature. FIG. 8 shows areference spectra 800 and experimental peaks 801 showing formation of2-hexanol. FIG. 9 shows a reference spectra 900 and an experimental peak901 showing formation of 3-hexanol. FIG. 10 shows a reference spectra1000 and experimental peaks 1001 showing formation of the aldehyde,hexanal. FIG. 11 shows experimental peaks 1101 showing formation of theketone, 2-hexanone. FIG. 12 shows a reference spectra 1200 andexperimental peaks 1201 showing formation of the ketone, 3-hexanone.

Tables 1 through 6 show the concentrations, production rates, and energyyields for all six identified species for various inlet flow rates andratios of organic to water in the feed. Typically the highest productionrates and energy yields occur at the lower organic to water flow rateratio (1.7E-2) for the cases with water flow rates of 0.5 ml/min,although for some cases the differences between water flow rates of 0.5and 1 ml/min are minor. Generally the production rates and energy yieldsdecrease as the ratio of organic to water flow rate increases, althoughfor some cases the values are lowest for intermediate ratios of organicto water.

TABLE 1 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 9.48E−06 9.48E−037.90E−05 1.5 1.90E−01 5.00E−01 1.25E−02 2.50E−02 5.51E−06 5.51E−034.59E−05 1.5 1.10E−01 5.00E−01 2.50E−02 5.00E−02 6.06E−06 6.06E−035.05E−05 1.5 1.21E−01 1.00E+00 1.67E−02 1.67E−02 4.52E−06 4.52E−037.53E−05 1.5 1.81E−01 1.00E+00 2.50E−02 2.50E−02 1.58E−06 1.58E−032.63E−05 1.5 6.32E−02 1.00E+00 5.00E−02 5.00E−02 3.48E−06 3.48E−035.80E−05 1.5 1.39E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+00

TABLE 2 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 2.38E−05 2.38E−021.98E−04 1.5 4.76E−01 5.00E−01 1.25E−02 2.50E−02 1.40E−05 1.40E−021.16E−04 1.5 2.79E−01 5.00E−01 2.50E−02 5.00E−02 9.34E−06 9.34E−037.78E−05 1.5 1.87E−01 1.00E+00 1.67E−02 1.67E−02 7.47E−06 7.47E−031.24E−04 1.5 2.99E−01 1.00E+00 2.50E−02 2.50E−02 2.42E−06 2.42E−034.04E−05 1.5 9.69E−02 1.00E+00 5.00E−02 5.00E−02 4.97E−06 4.97E−038.29E−05 1.5 1.99E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+005.00E−01 2.50E−02 5.00E−02 9.34E−06 9.34E−03 7.78E−05 1.5 1.87E−011.00E+00 1.67E−02 1.67E−02 7.47E−06 7.47E−03 1.24E−04 1.5 2.99E−01

TABLE 3 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 1.87E−05 1.87E−021.56E−04 1.5 3.75E−01 5.00E−01 1.25E−02 2.50E−02 1.01E−05 1.01E−028.43E−05 1.5 2.02E−01 5.00E−01 2.50E−02 5.00E−02 9.59E−06 9.59E−037.99E−05 1.5 1.92E−01 1.00E+00 1.67E−02 1.67E−02 8.67E−06 8.67E−031.44E−04 1.5 3.47E−01 1.00E+00 2.50E−02 2.50E−02 3.37E−06 3.37E−035.62E−05 1.5 1.35E−01 1.00E+00 5.00E−02 5.00E−02 4.63E−06 4.63E−037.72E−05 1.5 1.85E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+00

TABLE 4 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 9.92E−06 9.92E−038.26E−05 1.5 1.98E−01 5.00E−01 1.25E−02 2.50E−02 5.38E−06 5.38E−034.48E−05 1.5 1.08E−01 5.00E−01 2.50E−02 5.00E−02 8.51E−06 8.51E−037.09E−05 1.5 1.70E−01 1.00E+00 1.67E−02 1.67E−02 5.24E−06 5.24E−038.73E−05 1.5 2.10E−01 1.00E+00 2.50E−02 2.50E−02 2.54E−06 2.54E−034.24E−05 1.5 1.02E−01 1.00E+00 5.00E−02 5.00E−02 2.69E−06 2.69E−034.48E−05 1.5 1.07E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+00

TABLE 5 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 1.84E−05 1.84E−021.54E−04 1.5 3.69E−01 5.00E−01 1.25E−02 2.50E−02 9.18E−06 9.18E−037.65E−05 1.5 1.84E−01 5.00E−01 2.50E−02 5.00E−02 7.07E−06 7.07E−035.89E−05 1.5 1.41E−01 1.00E+00 1.67E−02 1.67E−02 5.42E−06 5.42E−039.03E−05 1.5 2.17E−01 1.00E+00 2.50E−02 2.50E−02 2.37E−06 2.37E−033.95E−05 1.5 9.48E−02 1.00E+00 5.00E−02 5.00E−02 2.77E−06 2.77E−034.61E−05 1.5 1.11E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+00

TABLE 6 Water Organic Production flow rate flow rate Ratio Conc. Conc.Rate Power Energy yield (mL/min) (mL/min) organic/water (M) (mM)(umol/s) (W) (mmol/kWh) 5.00E−01 8.30E−03 1.66E−02 3.48E−05 3.48E−022.90E−04 1.5 6.95E−01 5.00E−01 1.25E−02 2.50E−02 1.64E−05 1.64E−021.37E−04 1.5 3.29E−01 5.00E−01 2.50E−02 5.00E−02 1.52E−05 1.52E−021.27E−04 1.5 3.04E−01 1.00E+00 1.67E−02 1.67E−02 1.14E−05 1.14E−021.90E−04 1.5 4.55E−01 1.00E+00 2.50E−02 2.50E−02 5.74E−06 5.74E−039.56E−05 1.5 2.30E−01 1.00E+00 5.00E−02 5.00E−02 6.50E−06 6.50E−031.08E−04 1.5 2.60E−01 2.50E−01 2.50E−03 1.00E−02 0.00E+00 0.00E+00 1.50.00E+00 2.50E−01 4.10E−03 1.64E−02 0.00E+00 0.00E+00 1.5 0.00E+00

FIGS. 13 to 16 show the production rates as functions of the ratio oforganic to water flow rates for the alcohols, aldehydes, and ketones.Clearly variation of the relative flow rates of the hexane and wateraffect the production rate and lower ratios of hexane to water lead tohigher production rates of the organic products. The OH radical appearsto preferentially attack the tertiary carbon as indicated by the higherproduction rates of 3-hexanol and 3-hexanal in comparison to the primaryand secondary compounds. The preferential attack on the tertiary carbonis consistent with that seen in oxygen plasma reactions with hexane.FIG. 16 shows the production rate of hydrogen peroxide as functions ofthe organic content in the feed for various liquid water flow rates.Clearly, as the amount of organic increases relative to that of water,the amount of hydrogen peroxide measured in the liquid phase decreases.This is likely due to the competing reaction of OH radicals with theorganic relative to the recombination of the OH radical to form hydrogenperoxide. Clearly, significant hydrogen peroxide persists even in thepresence of relatively large amounts of organic compound and higherconcentrations of hydrogen peroxide occur with lower water flow ratesand this latter finding is consistent with our previous work in theabsence of hexane addition. The production rate of hydrogen peroxide isnot largely affected by the presence of the organic compound except atvery large molar ratios of organic to water.

FIG. 18 shows an example NMR spectrum demonstrating the presence ofreaction products from n-hexane. In this figure the bottom spectrumrepresents the unreacted starting material while the top spectrumrepresents the liquid effluent from the reactor after extraction.Comparison of these clearly shows the presence of both alcohol andketone products in the characteristic regions of the functional groups.The major products and their relative ratios as identified with NMR were3-hexanol (26%), 2-hexanol (21%), 3-hexanone (17%) and 2-hexanone (17%),1-hexanol (11%), hexanal (8%). A significant amount of unreactedn-hexane was also found. Additionally, the NMR analysis also suggeststhe presence of organic peroxides; however they could not be reliableassigned due to the relatively low stability. The NMR spectrum shows astarting material spectrum 181, corresponding to n-hexane and DI water;a product spectrum 182; an alcohol region 183; and a ketone region 184.

FIG. 19 depicts a gas chromatogram of the reaction products fromn-hexane. As with the NMR analysis the main products identified were1-hexanol (4.95 min) 191, 2-hexanol (3.90 min) 192, 3-hexanol (3.68 min)193, hexanal (2.81 min), 2-hexanone, hexanal (2.81 min) 194, and3-hexanone (2.60 min) 195. A chloroform peak 196 and an unidentifiedpeak 197 were also observed. It should be noted that separation of2-hexanone from hexanal was not achieved and the two compounds appear asone peak. Further, an additional peak appears at 4.52 min which couldnot been identified but may be accounted for by the suggested presenceof organic peroxides given in the NMR analysis.

A similar analysis was performed in order to assess the productsgenerated when cyclohexane was used as the organic feedstock instead ofn-hexane. A comparison of the major product distributions of the twoexperiments can be found in Table 7. More specifically, Table 7 showsmajor product distribution of the compounds formed from n-hexane (top)and cyclohexane (bottom) as well as percent conversion, overallproduction rate, and energy yield. All values presented on are on a permole bases.

TABLE 7 Total Mole Total organic percent organic product Mole of productenergy percent unreacted production yield conversion organic rate (mmol/Major product of organic collected (μmol/hr) kWh) distribution n-hexane1.7%  9.8% 15.4 30.8 3-Hexanol 26% 2-Hexanol 21% 3-Hexanone 17%2-Hexanone 17% 1-Hexanol 11% Hexanal  8% Cyclohexane 1.7% 21.9% 16.232.5 Cyclohexanone 47% Cyclohexene 20% Cyclohexanol 19% Hexanal 11%2-cyclohexenone  2%

When cyclohexane was utilized as the organic starting material the majorproducts identified and their relative distributions were cyclohexanone(47%), cyclohexene (20%), cyclohexanol (19%), hexanal (11%), and2-cyclohexenone (2%). As with the conversion of n-hexane, NMR analysisalso suggests the presence of organic peroxides (i.e., C₆H₁₁OOH) derivedfrom cyclohexane. In both experiments only a small fraction of theorganic starting material was functionalized, 1.7%. for n-hexane and2.0% for cyclohexane. While this is a small fraction it should be notedthat a large portion of the organic starting material not accounted forin the form of functionalized products does not undergo furtheroxidation but instead remains unreacted. This is evident from thesignificant amount of unreacted organic feed detected in the NMRanalysis; unfortunately, accurate quantification of these compounds wasnot possible due to the overlap of the compound's NMR signals with theNMR signals for the aliphatic parts of the products. None the less, arough quantification was determined showing approximately 10% of then-hexane starting material was collected and 22% for cyclohexane. Itshould be noted that additional organic starting material was detectedin the gas effluent after passage through both cold traps, and likelyaccounts for a large fraction of organic starting material notcollected, but could not be quantified with the instrumentationavailable. The fact that only a portion of the starting material waschemically modified and that most of the products generated were theresult of only one or two oxidative steps of the parent moleculeindicates that our reactor system provides soft activation, thusjustifying the viability of this set up for potential chemical synthesisroutes in partial oxidation of the alkanes.

When the distribution of products generated from the oxidation ofn-hexane is examined, the OH radical appears to preferentially attackthe C₂ and C₃ carbons of the n-hexane molecule as indicated by the lowerratios of 1-hexanol and hexanal in comparison to the ketones andsecondary alcohols. This -preferential attack is consistent with datareported in the literature for oxygen plasma reactions with n-hexane inDBD.

When the distribution of the products generated from the oxidation ofcyclohexane is examined it is clear that reaction selectivity is higherwhen compared to the oxidation of n-hexane as evident from the largeportion of cyclohexanone, 47%, found relative to the other products. Thefact that there is no distinction between carbons in the cyclohexanemolecule likely leads to this increase in selectivity. However, it isnot clear why the ketone product dominates when cyclohexane is utilizedwhile the alcohols dominate in the case of n-hexane. This result differsfrom those found when cyclohexane was oxidized with oxygen in DBD wherean almost equal ratio of cyclohexanone to cyclohexanol was produced. Itshould additionally be pointed out that the generation of cyclohexene islikely to result from the loss of hydrogen atom from cyclohexyl radical.It is known that β-C—H bond energy in the alkyl radicals is nearly afactor of 3 smaller than that in respective alkanes. Further, thisproduct was not reported in the above mentioned studies with oxygen inDBD.

The overall production rate and energy yield for the major productsgenerated are also given in Table 7. The energy yield for productsgenerated from n-hexane was found to be 8.6×10⁻⁹ mol/J and 9.0×10⁻⁹mol/J for cyclohexane. These values are approximately an order ofmagnitude lower than those found for the degradation of n-hexane andcyclohexane by oxygen plasma reactions in DBD where the authors reported1.1×10⁻⁷ and 1.9×10⁻⁷ mol/J respectively. However, it should be notedthat this does not represent the total energy yield for all generatedproducts because hydrogen peroxide is also produced at an energy yieldof 0.54 mol/kWh (1.5×10⁻⁷ mol/J).

Table 8 shows the individual production rates and energy yields for allproducts generated in the experiments. More specifically, Table 8 showsindividual production rates and energy yields for the generated productsproduced as well as the relative distribution of where the products werecollected. All values presented are on a per mole bases.

TABLE 8 Mole Mole Pro- Mole percent Percent duction Energy percentcollected collected rate yield collected in in (μmol/ (mmol/ in liquidprimary secondary Compound hr) kWh) effluent cold trap cold trapn-hexane n-Hexane n/a n/a  0% 19% 81% 1-Hexanol 1.6 3.3  48% 22% 31%2-Hexanol 3.2 6.4  47% 24% 29% 3-Hexanol 4.0 8.1  44% 20% 36% Hexanal1.3 2.5  38% 17% 45% 2-Hexanone 2.6 5.3  40% 21% 39% 3-Hexanone 2.7 5.3 32% 27% 41% Hydrogen 273 545 100%  0%  0% Peroxide CyclohexaneCyclohexane n/a n/a  0%  0% 100% Cyclohexene 3.3 6.6  0%  0% 100%Cyclohexanone 7.6 15.2  54% 14%  32% Cyclohexanol 3.1 6.3  42% 16%  43%Hexanal 1.8 3.6  6%  2%  93% 2-cyclohexenone 0.4 0.8  80%  9%  11%Hydrogen 259 518 100%  0%  0% peroxideTable 8 also provides a breakdown of where the generated products werecollected, i.e. the relative ratios of products in the three separateliquid fractions which were collected and extracted. One of the moreimportant generalizations of Table 8 is that no n-hexane, cyclohexane,or cyclohexene was detected in the liquid effluent collection vessel andconversely no hydrogen peroxide was detected in either the primary orsecondary cold traps. This result can be explained by the vastlydifferent vapor pressures and water solubility of these organiccompounds compared to hydrogen peroxide, in that the high watersolubility of hydrogen peroxide as well its relativity low vaporpressure allow the product to be rapidly dissolved into the liquid waterphase leaving no detectable amounts vaporized in the flowing argon gas.In contrast, the high volatility and low solubility in water ofn-hexane, cyclohexane, and cyclohexene hinders them from dissolving intothe liquid effluent making these compounds difficult to collect. Aspreviously mentioned it is likely a significant amount of these volatilecompounds is still present in the gas effluent of the secondary coldtrap. This result demonstrates the importance of the relative chemicalproperties of the products of interest to those of the liquid absorbent,which is in this case water. Because the volatility and solubility ofthe other major products lies between the extremes of the previouslymentioned organic compounds and hydrogen peroxide, these compounds arecollected in both the liquid effluent and cold traps. As a result, it isreasonable to conclude that almost all of the hydrogen peroxide producedin the reactor is collected but a portion of the other organic productsgenerated as well as a large amount of unreacted starting material mayremain vaporized in the argon gas even after subjection to two coldtraps. Our future experiments will determine whether it is possible toimprove overall yield by choosing a parent compound whose oxidativeproducts are more soluble in water and less volatile.

Additional experiments were conducted to determine the radicalscavenging potential of increasing amounts of organic starting materialin order to assess the impact on the production rate of hydrogenperoxide. In these experiments the water flow rate was held constant at0.5 mL/min while the n-hexane flow rate was varied from 0 to 0.002,0.005, 0.01, 0.02, and 0.04 mL/min. The values for hydrogen peroxideproduction rate as well as the discharge power under these conditionsare shown in FIGS. 20a and 20 b.

FIG. 20a shows that as the amount of n-hexane added to the reactor wasincreased, the power of the discharge also increased. FIG. 20b shows theproduction rate of hydrogen peroxide increased from the case with purewater when only a very small amount of n-hexane (0.002-0.005 mL/min) wasadded to the reactant feed. This increase can be explained by the slightincrease in power that occurred when the n-hexane was added to the gasphase. The result also shows that when only a small amount of n-hexaneis added to the reactant feed the hydroxyl radical reactions with theorganic compounds do not affect the hydrogen peroxide formation rate.When this experiment was performed with cyclohexane as the organicstarting material almost identical trends were found. It is possiblethat the hydroxyl radical reactions which produce the hydrogen peroxideoccur very close to the liquid-gas interface, and thus are unaffected bygas phase organic radical scavengers at low enough concentration. Thishypothesis is supported by the fact that when the ratio of organic towater was increased further, the production rate of hydrogen peroxidedecreased even though the discharge power continued to increase. Asimilar finding, whereby increasing radical probe concentration reducedhydrogen peroxide formation, was found in a pulsed corona dischargedirectly in liquid water.

Lastly, there was no visual evidence of polymerization products in thepresent experiments further justifying that over oxidation wasprevented. However, additional analysis of the gas effluent is necessaryto determine if there is indeed additional product still vaporized inthe argon and to quantify the remaining starting material in this phasein order to close the mass balance.

The results of this study clearly show that chemical synthesis byoxidation with hydroxyl radicals is possible with the reactor systemdescribed in this paper. Significant amounts of alcohol, ketone, andaldehyde products were produced from both n-hexane and cyclohexane afterattack on the molecules by hydroxyl radicals produced from the liquidwater phase contacting the plasma. This work also proves that someselectivity of the reaction products can be gained by the choice of aparent compound, and also suggests that it may be possible to furthercontrol selectivity with alterations to such experimental conditions aswater flow rate, organic to water feed ratio, reactor pressure, andpulse parameters. Additionally, substantial amounts of hydrogen peroxidewere also produced despite the addition of the organic compounds to thereactor feed which have been shown to act as gas phase radicalscavengers at high enough concentrations. It was also found that theselection of a parent compound which yields chemical species with a lowvolatility and a high solubility in water upon oxidation could makecollection of the generated products easier and increase the overallyield of the process. Finally, due to the high concentration of hydrogenperoxide produced in conjunction with the other major functionalizedproducts, additional work is warranted to capitalize on this aspect ofthe system.

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the preferred versions containedherein.

All the features disclosed in this specification (including anyaccompanying claims, abstract, and drawings) may be replaced byalternative features serving the same, equivalent or similar purpose,unless expressly stated otherwise. Thus, unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features.

Any element in a claim that does not explicitly state “means for”performing a specified function, or “step for” performing a specificfunction, is not to be interpreted as a “means” or “step” clause asspecified in 35 U.S.C § 112, sixth paragraph. In particular, the use of“step of” in the claims herein is not intended to invoke the provisionsof 35 U.S.C § 112, sixth paragraph.

1.-32. (canceled)
 33. A reactor comprising: a body portion having one ormore internal walls that define an internal cavity, at least oneelectrically-conductive inlet capillary having an inlet capillary bodyextending between a fluid-receiving tip and a fluid-injecting tip,wherein the fluid-receiving tip is positioned outside the internalcavity, and wherein the fluid-injecting tip is positioned inside theinternal cavity; at least one electrically-conductive outlet capillaryhaving an outlet capillary body extending between a fluid-collecting tipand a fluid-ejecting tip, wherein the fluid-collecting tip is positionedinside the internal cavity, and wherein the fluid-ejecting tip ispositioned outside the internal cavity; and a power source, supplying avoltage across the at least one electrically-conductive inlet capillaryand the at least one electrically-conductive outlet capillary, whereinthe fluid injecting tip is disposed relative to the fluid collecting tipto generate a flowing liquid film region on the one or more internalwalls and a gas stream flowing through the flowing liquid film region,when a fluid is injected into the internal cavity via the at least oneelectrically conductive inlet capillary; wherein the fluid injecting tipis disposed relative to the fluid collecting tip to propagate a plasmadischarge along the flowing liquid film region between the at least oneelectrically-conductive inlet capillary and the at least oneelectrically-conductive outlet capillary.
 34. The reactor according toclaim 33, wherein the fluid injecting tip is aligned with the fluidcollecting tip.
 35. The reactor according to claim 33, wherein the powersource is adapted to provide a pulsed current between the at least oneelectrically-conductive inlet capillary and the at least oneelectrically-conductive outlet capillary.
 36. The reactor according toclaim 33, wherein the power source is adapted to provide a D.C. currentbetween the at least one electrically-conductive inlet capillary and theat least one electrically-conductive outlet capillary.
 37. The reactoraccording to claim 33, wherein the power source is adapted to provide anA.C. current between the at least one electrically-conductive inletcapillary and the at least one electrically-conductive outlet capillary.38. The reactor according to claim 33, wherein a gap separates thefluid-injecting tip and the fluid-collecting tip, wherein the gap has alength, and wherein a ratio of the voltage to the length is at leastabout 2.5×10⁵ V/m.
 39. The reactor according to claim 33, wherein thebody portion is cylindrical, wherein the body portion has a firstdiameter of from 1 mm to 1 cm, wherein the at least oneelectrically-conductive inlet capillary has a second diameter that isless than the first diameter, and wherein the at least oneelectrically-conductive outlet capillary has a third diameter that isgreater than the second diameter and less than the first diameter.
 40. Areactor system comprising: an electrically-conductive inlet capillarytube electrode for simultaneously charging a liquid and gas inside theelectrode, the electrically-conductive inlet capillary tube electrodehaving a first internal diameter; a tubular plasma reactor having asecond internal diameter and having one or more internal walls; anelectrically conductive outlet capillary tube electrode having a thirdinternal diameter, the third internal diameter being larger than thefirst internal diameter and smaller than the second internal diameter; apower source for supplying a voltage across the at least oneelectrically-conductive inlet capillary tube and the at least oneelectrically-conductive outlet capillary tube; theelectrically-conductive inlet capillary tube electrode being configuredto inject a charged mixture comprising a liquid and a gas into theplasma reactor, the injecting of the charged liquid and gas generating acontinuously flowing liquid film region on one or more internal walls,and a gas stream flowing along the flowing liquid film region, theinjecting further propagating a plasma discharge channel pattern alongthe interface between the flowing liquid film region and the flowing gasstream inside the plasma reactor; the reactor dissociating at least aportion of the liquid at the interface with the plasma discharge to formdissociation products; the reactor producing a reaction product from thedissociation products, the reaction product dissolving into the flowingliquid film region; and flowing the liquid, gas, plasma, and reactionproduct to the electrically conductive outlet capillary tube electrode.41. The reactor system of claim 40, wherein the liquid comprises waterand the reaction product comprises hydrogen peroxide.
 42. The reactorsystem of claim 40, wherein the power source provides a plasma dischargethat is a pulsed discharge.
 43. The reactor system of claim 40, whereinat least one organic compound is injected with the liquid and the gasinto the at least one electrically conductive inlet capillary tubeelectrode.